Segment of a Solar Collector and Solar Collectors

ABSTRACT

A segment of a solar collector including a top side, a bottom side and a circumferential end face having at least one longitudinal side, wherein the longitudinal side forms a top edge with the top side and forms a bottom edge with the bottom side, and comprises a core structure having at least one core made of foamed material. The segment of a solar collector further includes a shell made of one or a plurality of layers of a fiber material, wherein the shell at least partially covers the top side, the bottom side and at least the longitudinal side of the circumferential end face, wherein at least one layer of the shell extends about the top edge and at least one layer of the shell extends about the bottom edge, and a reflection layer disposed on the top side.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 13/383,926 filed on Jun. 14, 2010 which is theUnited States national phase of International Application No.PCT/EP2010/058284 filed Jun. 14, 2010, and claims priority to GermanPatent Application No. 10 2009 033 490.4 filed Jul. 15, 2009, thedisclosures of which are hereby incorporated in their entirety byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the design of solar collectors and thedesign of segments of a solar collector. Solar collectors are often usedin the form of parabolic-trough concentrators in power plants, or forrecovery of process heat.

2. Description of Related Art

Such large-scale plants can largely consist of a plurality of seriallyarranged solar collectors with trough-shaped reflectors which willdirect the sunlight onto a tubular absorber. For orienting the solarcollectors corresponding to the sunlight, it is known to rotate thetrough-shaped reflectors about their longitudinal axis. In order toreduce the apparatus-related expenditure when using this approach, it ismostly provided that, with the aid of a drive unit, a plurality ofserially arranged reflectors are rotated simultaneously.

Since, in this manner, constructions having a length of up to 120 m areto be rotated, the trough-shaped reflectors must have a high torsionalstiffness so that the deviation of the rotational angle during rotationof the reflectors cannot exceed a mere minimum.

In the past, for this reason, solar collectors were often built fromsteel constructions with mirrors mounted thereon, however at the penaltyof a massive weight of the solar collectors. Further, complex supportstructures were required, and the weight resulted in high costs fortransportation. Frequently, the reflectors had to be built in situ fromindividual components, thus causing considerable assembly work at theinstallation site.

Solar collectors of lightweight construction often have the disadvantagethat their structure has insufficient self-supporting properties, withthe consequence that a large number of supports are required and or thatthe solar collectors can be only quite small in size.

Thus, it is an object of the present invention to provide a segment of asolar collector which allows for a solar collector with light-weighteddesign, high torsional stiffness and self-supporting structure, whilealso the assembly work in situ is to be kept small.

Further, it is an object of the present invention to provide a solarcollector having a light-weighted design and a self-supportingstructure.

SUMMARY OF THE INVENTION

According to the invention, it is provided that a segment of a solarcollector comprises a top side, a bottom side and a circumferential endface having at least one longitudinal side, wherein the longitudinalside forms a top edge with the top side and forms a bottom edge with thebottom side. The segment further comprises a core structure having atleast one core made of foamed material. Arranged on the core structureis a shell made of one or a plurality of layers of a fiber material,wherein the shell at least partially covers the top side, the bottomside and at least the longitudinal side of the circumferential end face,and wherein at least one layer of the shell extends about the top edgeand at least one layer of the shell extends about the bottom edge. Thesegment further comprises a reflection layer disposed on the top side.

The use of a core structure comprising at least one core of foamedmaterial makes it possible to accomplish a particularly light-weighteddesign of the segment and thus of a solar collector. The shellcomprising one or a plurality of layers of a fiber material has theeffect that the segment is given sufficient stability.

With the aid of the longitudinal side, two adjacent segments can beconnected to each other, wherein the shell of a segment that extendsabout the top edge and the bottom edge in combination with the shell ofan adjacent segment that extends about the top edge and the bottom edge,forms a kind of profile carrier shaped as a double T.

In this manner, there is obtained a considerably high structuralstrength of a solar collector consisting of the segments according tothe invention. Particularly, this effect is intensified if two adjacentsegments are bonded to each other since, in this manner, the twolikewise bonded shells of the adjacent segments will be connected toeach other by substance-to-substance bonding and thus will form aparticularly firm structure. By using a fiber material for the shell,the bonding of the adjacent segments will establish a support structureof the fiber material that can be considered as forming virtually oneintegral piece, which is the case because the fiber material can besoaked by the adhesive. Thus, the segments according to the inventioncan be assembled into solar collectors having a self-supportingstructure, so that the solar collectors can have a large length withoutthe need for additional support elements.

According to a preferred embodiment, it is provided that the shellconsists of at least one first shell member made of a fiber materialthat is arranged on the top side and covers the core structure on thetop side, and of a second shell member made of a fiber material that isarranged on the bottom side and covers the core structure on the bottomside.

In this manner, the shell of the core structure can be produced in asimple manner.

In the above arrangement, it can be provided that the first shell memberextends around the top edge and/or the second shell member extendsaround the bottom edge. In a segment according to the invention whichcomprises two or more longitudinal sides of the surrounding end face,via which the segment can be connected to other segments, it can beprovided that the shell member extends around the top edges of alllongitudinal sides while the second shell member extends around thebottom edges of all longitudinal sides. By the provision of a first anda second shell member, the inventive shell of the core structure can beproduced in a simple manner, while at the same time advantageouslysafeguarding the desired extension of the shell around the top edge andaround the bottom edge.

Additionally or alternatively thereof, it can be provided that the shellcomprises a third shell member made of a fiber material that is arrangedon the at least one longitudinal side and covers the core structure onthe longitudinal side, said third shell member extending around the topedge and/or the bottom edge. The first, the second and/or the thirdshell member can respectively consist of at least one layer of fibermaterial, preferably of at least two layers of fiber material and withparticular preference of three layers of fiber material. Particularly,it is provided that the layers of the shell are made of glass-fiber orcarbon-fiber material and comprise unidirectional or multi-axial fibers.

Thereby, the desired strengthening effect of the shell can be achievedin an advantageous manner. By use of said layers of unidirectional ormulti-axial fibers, the segments can be given high resistance to ruptureand high torsional stiffness while, at the same time, a solar collectorcomposed of the segments according to the invention can have aparticularly advantageous self-supporting structure. This can beaccomplished particularly by selecting, for different layers of theshell, materials with different fiber directions, since the fiberdirection can be selected corresponding to the respective stressdirection of the segments.

According to a preferred embodiment, it is provided that reinforcementstrips of fiber material are arranged around the top edge, the bottomedge and/or around the further edges formed between the surrounding endfaces and the top side and the bottom side, so as to reinforce the topedge, the bottom edge and the further edge of the core structure.

According to a particularly preferred embodiment, it is provided thatthe core structure comprises at least one rib of a fiber material,preferably of wood, said rib being preferably arranged parallel to theat least one longitudinal side. Such a rib is effective to increase thestability of the core structure.

In the above arrangement, it can be provided that the core structureconsists of two cores of foamed material and of three ribs of fibermaterial, said ribs and said cores of foamed material being arrangedalternately. In other words: The core structure consists of two cores offoamed material, which cores are enclosed by two ribs, with a furtherrib being arranged between the cores of foamed material. The two outerribs herein are arranged respectively on one of the longitudinal sides.Such a configuration has proven to be particularly advantageous.

It can be provided that each rib comprises a cover made of a fibermaterial, thus allowing for a very high stability of the ribs.

According to one embodiment of the invention, it is provided that,adjacent to the longitudinal side, a flange is arranged for attachmentof the segment to an opposite segment. When assembling a solar collectorfrom segments according to the invention, flanges arranged on thesegments for mutual attachment of opposite segments have been found tobe of particular advantage. In this manner, a plurality of segmentsserially fastened via the longitudinal sides of the segments can beconnected, with the aid of the flanges, to a further row of flanges. Inthis regard, it can be provided that the flanges are a part of theoverall structure of the segment and thus are formed by the corestructure and the shell.

The top side of the core structure can have a curvature so that thereflection layer on which there is arranged the part of the shellcovering the top side of the core layer, is also curved. In this manner,the segments according to the invention can be assembled toparabolic-trough-shaped or parabolic solar collectors.

The layers of the shell, the at least one core of foamed material, theribs of the core structure, the shell of the ribs, and/or thereinforcing strips can be bonded to each other, preferably by means ofan epoxy resin adhesive or another resin-based adhesive such as e.g.polyester or polyvinyl resin. The mutual bonding of the individualcomponent parts of a segment according to the invention advantageouslyallows for a particularly tight connection between the individualcomponent parts. The use of an epoxy resin adhesive has the benefit thatthis adhesive will become connected in an advantageous manner to thelayers of the shell consisting of fiber material, and to the ribs madeof fiber material, particularly if the fiber material ribs consist ofwood. In this manner, it is advantageously rendered possible for theadhesive to become anchored to the respective material. When usingglass-fiber or carbon-fiber material for the layers of the shell, thematerial will advantageously be soaked by the epoxy adhesive, thusgenerating a structure of epoxy resin and glass fibers or carbon fiberswhich has a high stability. When bonding different layers of the shellof a segment or of adjacent segments, the use of the epoxy adhesivemakes it possible to bond the layers to each other in such a manner thatthey can nearly be regarded as being one integral piece.

The object forming the basis of the invention is further achieved by asolar collector comprising a plurality of segments according to theinvention.

In this regard, it is preferably provided that, in the solar collector,two adjacent segments are bonded to each other via the longitudinalsides and that a row of mutually bonded segments can be connected, withthe aid of the flanges, to a further row of opposite segments.

Such a solar collector can be conveniently produced and be transportedto its installation site in that a row of adjacent segments are bondedto each other already at the production site and in situ merely have tobe connected to a further row of segments according to the invention.

The solar collectors composed of the segments according to the inventionare very light-weighted and thus transportable in a convenient manner.Further, the solar collectors have a high torsional stiffness andcomprise a self-supporting structure.

According to a particularly preferred embodiment, it is provided thattwo rows of adjacent segments are connected to each other via saidflanges, there further being provided a U-profile enclosing the flanges.Said U-profile can consist e.g. of a plurality of layers of fibermaterial which are bonded to each other preferably by an epoxy resinadhesive. It has been found that the use of a U-profile makes itpossible to achieve a particularly high torsional stiffness of the solarcollector. The solar collector according to the invention can consist ofe.g. 24 segments according to the invention.

According to one embodiment of the invention, it is provided that aframework construction is arranged on the surface formed by the bottomside of the segments so as to increase the torsional stiffness, saidframework construction being attached to the bottom side of the solarcollector preferably via fastening means bonded between two adjacentsegments.

The framework construction can be connected e.g. to a support structureof an absorber. Another option resides in that the frameworkconstruction of the solar collector is preferably connected to anattachment metal plate of a solar collector support. In this manner, itcan be safeguarded that a very high stability of the frameworkconstruction is achievable.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained in greater detail hereunder withreference to the accompanying Figures. In the Figures, the following isshown:

FIG. 1 is a schematic representation of an inventive segment of a solarcollector,

FIG. 2 is a schematic sectional view of the segment shown in FIG. 1,

FIG. 3 is an enlarged schematic sectional view of an inventive segment,

FIG. 4 is a schematic sectional view of two adjacent inventive segments,

FIG. 5 is a schematic sectional view of an inventive solar collector,and

FIG. 6 is a schematic perspective view of an inventive solar collector.

DETAILED DESCRIPTION OF THE INVENTION

In FIG. 1, an inventive segment 1 of a solar collector is schematicallyillustrated. Said segment 1 comprises a top side 2, a bottom side 4 anda surrounding end face 6 having two longitudinal sides 8. Thelongitudinal sides 8 together with the top side 2 form a respective topedge 10 and, together with the bottom side 4, a respective bottom edge12. At least the top side 2 of the segment is curved, wherein the uppersurface is provided with a reflective layer 14 adapted to reflectincident sunlight.

Via said longitudinal sides 8, a plurality of segments 1 according tothe invention can be connected to each other to form a row of segments1, e.g. by mutual bonding of the segments on the longitudinal sides 8.

Adjacent to the longitudinal sides 8, the segment 1 according to theinvention comprises a flange 16 by which the inventive segment 1 can beconnected to an opposite segment of identical design.

In FIG. 2, the segment according to FIG. 1 is schematically shown insectional view. Segment 1 comprises a core structure 20 enclosed by ashell 22.

Said core structure 20 consists of two cores 24 made of foamed material,and of ribs 26 made of a fiber material. Said ribs 26 can be producede.g. of wood or a wood-like material. Preferably, the ribs 26 are madeof Australian pine since this type of wood has a particularly highstiffness.

The ribs 26 are each provided with a cover 28 made of a fiber material.Two of the ribs 26 are arranged on the longitudinal sides 8 of segment 1so that the ribs enclose the cores 24 of foamed material. The third rib26 with cover 28 is arranged between the cores 24 of foamed material.

Said cover 28 made of fiber material increases the stability of the ribs26.

Said shell 22 enclosing the core structure 20 can consist of one or aplurality of layers of fiber material.

In the embodiment depicted in FIG. 2, shell 22 consists of a first shellmember 30 and a second shell member 32, each of them made of a layer offiber material. The first shell member 30 is arranged on the top side 2and covers the core structure 20 on the top side 2, while the secondshell member 32 is arranged on the bottom side 4 and covers the corestructure 20 on the bottom side 4. In this arrangement, the first shellmember 30 extends around the top edges 10 formed between thelongitudinal sides 8 and the top side 2, while the second shell member32 extends around the bottom edges 12 formed between the longitudinalsides 8 and the bottom side 4. The first shell member 30 and the secondshell member 32 can consist of one or a plurality of layers of a fibermaterial.

Since the first shell member 30 and the second shell member 32 extendaround the top edge 10 and the bottom edge 12, the bonding connection ofthe inventive segment 1 to a further inventive segment 1 via therespective longitudinal sides 8 will generate a stable structure fromthe respective shells 22 of the inventive segments 1. In this manner,there can be formed solar collectors which have a self-supportingstructure and further have a high torsional stiffness and breakageresistance.

On the top side 2 of the inventive segment 1, a refection layer isarranged, not shown in FIG. 2.

In FIG. 3, the region around the longitudinal sides 8 of an inventivesegment 1 is schematically shown in enlarged sectional view.

The embodiment shown in FIG. 3 substantially has the same structure asthe embodiment of an inventive segment 1 shown in FIG. 2. The essentialdifference resides in that the first shell member 30 consists of threelayers 30 a-30 c while the second shell member 32 consists of threelayers 32 a-32 c. The layers 30 a-30 c and respectively 32 a-32 c eachconsist of a fiber material, e.g. a glass fiber material. These can beapplied in the form of glass fiber mats. In this regard, it can beprovided e.g. that the layers 30 c and 32 c facing toward core structure20 consist of a glass fiber material comprising multi-axially orientedfibers, whereas the outer layers 30 a,30 b,32 a,32 b consist of a glassfiber material comprising unidirectional fibers. Further, reinforcementstrips 34 are provided which are arranged on the top edge 10 and thebottom edge 12 and reinforce the edges of the core structure 20. Alsosaid reinforcement strips 34 can consist of a fiber material.

When producing the inventive segment 1, the ribs 26 will first be bondedto the shell 28 with the aid of an adhesive, preferably an epoxy resinadhesive. The individual layers of the second shell member 32 will alsobe bonded with the aid of an adhesive, preferably an epoxy resinadhesive, and the core structure 20 will be arranged on the second shellmember 32. In case it is intended to use reinforcement strips 34, thesecan be inserted and also bonded prior or subsequent to the placement ofthe core structure 20. Then, the individual layers of the first shellmember 30 will be applied and bonded. By the use of a fiber material forthe individual layers of the shell members 30 and 32, the shell members,if an epoxy resin adhesive is used, will be advantageously soaked by theepoxy resin adhesive, so that a very good connection will be effectedbetween the individual layers. The substance-to-substance bond betweenthe individual layers is of such a good quality that the shellconsisting of the individual layers can be considered as forming oneintegral piece.

Uneven spots or free spaces as caused e.g. by the reinforcement strips34 can be compensated for, or filled, by the adhesive material.

In FIG. 4, two mutually bonded inventive segments 1 are schematicallyillustrated in sectional view.

The two inventive segments 1 are bonded to each other via thelongitudinal side 8. The segments 1 substantially have the structureshown in FIGS. 2 and 3. The shell 22 of the segments 1 can consist of aplurality of layers of fiber material. By the bonding of the segments 1on the longitudinal side 8, the fiber material of shell 22 is soaked bythe adhesive, preferably an epoxy resin adhesive, thus generating a verygood connection between the shells 22 of the individual segments.

The substance-to-substance connection obtained by the bonding isexcellent enough for allowing the two shells of the two segments 1 to beconsidered as one integral piece, as indicated by the interrupted linein FIG. 4. In this manner, the shells 22 of the mutually bonded segments1 are combined to a support structure shaped as double T. Achievedthereby is a particularly high stability of a solar collector composedof a plurality of segments 1, while the solar collector is given anadvantageous self-supporting structure as a result of the bonded shell22.

Due to the materials used for the inventive segments, it is madepossible to assemble the inventive segments into a solar collector oflow weight and high stability.

The inventive segments can be reinforced by further layers of fibermaterial which are located in regions of elevated mechanical stress. Forinstance, the flange can be reinforced by added layers.

In FIG. 5, a solar collector 100 according to the invention isschematically depicted in sectional view, while the interior structureof the sectioned segments 1 is not shown. In FIG. 6, a solar collector100 according to the invention is schematically depicted in perspectiveview. In the view of FIG. 6, the solar collector 100 is presented in astrongly pivoted position.

The solar collector 100 consists of a plurality of interconnectedsegments 1, wherein adjacent segments 1 are connected via thelongitudinal sides 8 to thus form a row of segments 1. With the aid ofthe flanges 16 of the segments 1, two rows of segments 1 are assembledinto a parabolic trough. As evident from FIG. 6, a solar collector canconsist of 24 segments 1.

The flanges 16 are enclosed by an elongated U-profile 36 whereby thesize of the flanges 16 can be kept small and the torsional stiffness ofthe solar collector 100 can be improved. Said U-profile 36 can consistof a plurality of mutually bonded fiber material layers. The two rows ofsegments 1 and the U-profile 36 can be bolted or bonded to each other.

Arranged at the respective ends of solar collector 100 are solarcollector supports 38 on which the solar collector is rotatablysuspended via attachment metal plates 40. In this arrangement, it can beprovided that a plurality of solar collectors 100 are arranged behindeach other in a row and connected to each other, so that a plurality ofsolar collectors 100 can be rotated by a common drive unit for adjustingthe solar collectors to the altitude of the sun.

In the focus of the parabolic troughs formed by the segments 1, atubular absorber 42 is arranged, which is supported by a supportstructure 44. In operation, the medium to be heated will flow throughabsorber 42.

On the bottom side of solar collector 100 formed by the bottom sides 4of the segments 1, a framework construction 46 is arranged for improvingthe torsional stiffness of solar collector 100. With the aid offastening means, not shown in FIGS. 5 and 6, said framework construction46 can be attached to the surface formed by the bottom sides 4 of thesegments 1, wherein said fastening means can e.g. be bonded between twoadjacent segments and/or be bolted to the ribs—not shown in FIGS. 5 and6—of segments. The framework construction is further connected toU-profile 36 and said attachment metal plate 40. Further still, theframework construction 46 is connected to the support structure 44 ofabsorber 42. Obtained in this manner is a very high stability andtorsional stiffness of the solar collector 100 of the invention. Thetorsional stiffness herein is so high that, in a row of a plurality ofsolar collectors 100 of a length of 120 mm, a rotary movement will causea rotary deviation of the solar collectors of merely 5 millirad.

The framework construction 46 is preferably made of a stable material,e.g. steel.

The inventive segments advantageously allow for the production of verylight-weighted solar collectors having a self-supporting structure andalso a very high torsional stiffness. Already at the factory site, aplurality of inventive segments can be bonded to form a row of segmentsso that, at the installation site, these segments merely have to beconnected to a further row of segments via the flanges. In this regard,it has been observed segments of a width of up to 12 can be bondedtogether at the factory site without entailing transport problems.

The solar collectors of the invention can have a length of up to 12 mand an aperture of 4.60 m.

1. A segment of a solar collector comprising: a top side, a bottom sideand a circumferential end face having at least one longitudinal side,the longitudinal side forming a top edge with the top side and forming abottom edge with the bottom side, a core structure having at least onecore made of foamed material, a shell made of one or a plurality oflayers of a fiber material, and a reflection layer disposed on the topside, wherein the shell comprises a first shell member arranged on thetop side that at least partially covers the core structure on the topside and a second shell member arranged on the bottom side that at leastpartially covers the core structure on the bottom side, and wherein thefirst shell member wraps around the top edge to partially cover the atleast one longitudinal side and the second shell member wraps around thebottom edge to partially cover the at least one longitudinal sidewherein the first shell member and the second shell member togethercompletely cover the at least one longitudinal side.
 2. (canceled) 3.(canceled)
 4. The segment according to claim 1, wherein the shellcomprises a third shell member made of a fiber material that is arrangedon the at least one longitudinal side and covers the core structure onthe longitudinal side, the third shell member wrapping around the topedge and the bottom edge to at least partially cover the top side andthe bottom side.
 5. The segment according to claim 4, wherein the first,the second and the third shell members respectively comprise at leastone layer of fiber material.
 6. The segment according to claim 1,wherein the layers of the shell are made of glass-fiber or carbon-fibermaterial and comprise unidirectional or multi-axial fibers.
 7. Thesegment according to claim 1, wherein a reinforcement strip of fibermaterial is arranged around the top edge, the bottom edge and around thefurther edges formed between the surrounding end face and the top sideand the bottom side, so as to reinforce the top edge, the bottom edgeand the further edges.
 8. The segment according to claim 1, wherein thecore structure comprises at least one rib of a fiber material that isseparate from the core.
 9. The segment according to claim 8, wherein thecore structure comprises two cores of foamed material and three ribs,the ribs and the two cores of foamed material being arrangedalternately.
 10. The segment according to claim 8, wherein each ribcomprises a cover made of a fiber material that covers at least a topside and a bottom side of the rib.
 11. The segment according to claim 1,wherein, adjacent to the longitudinal side, a flange is arranged forattachment of the segment to an opposite segment.
 12. The segmentaccording to claim 1, wherein the top side has a curvature.
 13. Thesegment according to claim 10, wherein the layers of the shell, the atleast one core of foamed material, the ribs of the core structure, theshell of the ribs, and reinforcing strips are bonded to each other by anepoxy resin adhesive.
 14. A solar collector comprising a plurality ofsegments according to claim
 1. 15. The solar collector according toclaim 14, wherein two adjacent segments are bonded to each other via thelongitudinal sides and, wherein a row of mutually bonded segments can beconnected, with the aid of flanges on the segments, to a further row ofopposite segments.
 16. The solar collector according to claim 15,comprising two rows of segments connected to each other via the flangesof the segments, and by a U-profile enclosing the flanges.
 17. The solarcollector according to claim 16, wherein the U-profile comprises aplurality of layers of fiber material which are bonded to each other.18. The solar collector according to claim 14, comprising of 24segments.
 19. The solar collector according to claim 14, wherein aframework construction for increasing the torsional stiffness isarranged on the surface formed by the bottom side of the segments, theframework construction being attached to the solar collector.
 20. Thesolar collector according to claim 19, wherein the frameworkconstruction is connected to a support structure of an absorber.
 21. Thesolar collector according to claim 20, wherein the frameworkconstruction is connected to the support structure of the solarcollector.
 22. The segment according to claim 5, wherein the first, thesecond and the third shell members respectively comprise at least twolayers of fiber material.
 23. The segment according to claim 5, whereinthe first, the second and the third shell members respectively comprisethree layers of fiber material.
 24. The segment according to claim 8,wherein the rib is arranged parallel to the at least one longitudinalside.
 25. The segment according to claim 8, wherein the rib is made ofwood.
 26. The solar collector according to claim 17, wherein theplurality of layers of fiber material are bonded to each other by aresin-based adhesive.
 27. The solar collector according to claim 17,wherein the plurality of layers of fiber material are bonded to eachother by an epoxy resin adhesive.
 28. The solar collector according toclaim 19, wherein the framework construction is attached to the solarcollector via fastening means bonded between two adjacent segments. 29.The solar collector according to claim 21, wherein the frameworkconstruction is connected to an attachment metal plate of a solarcollector support.